Method of in-situ heat seal sleeving for large rolls

ABSTRACT

Heat sealing organic polymeric materials, especially fluorocarbon films, to form tubular sleeves about large and elongated rolls prior to heat-shrinking the sleeve snugly about the roll, thereby to effect rapid in-situ roll sleeving.

qfiuly 30, 1974 H. s. CHAPMAN METHOD OF IN-SITU HEAT SEAL SLEEVING FORLARGE ROLLS Filed Avril 21, 1972 2 Sheets-Ghee; 1.

Power July 30, 1974 s. CHAPMAN METHOD OF IN-SITU HEAT SEAL SLEEVING FORLARGE 'ROLLS Filed April 21. 1972 2 Sheets-Sheet B United States Patent3,826,702 METHOD OF IN-SITU HEAT SEAL SLEEVING FOR LARGE ROLLS HarrySamuel Chapman, RD. 3, Box 328, Hickory Hill, Oxford, Pa. 19363Continuation-impart of application Ser. No. 824,411, May 13, 1969, nowPatent No. 3,660,210. This application Apr. 21, 1972, Ser. No. 246,268

Int. Cl. B65h 8/00 US. Cl. 156--86 14 Claims ABSTRACT OF THE DISCLOSUREHeat sealing organic polymeric materials, especially fluorocarbon films,to form tubular sleeves about large and elongated rolls prior toheat-shrinking the sleeve snugly about the roll, thereby to effect rapidin-situ roll sleeving.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuationin-part application of parent application Ser. No. 824,411,filed May 13, 1969, now Pat. No. 3,660,210.

THE INVENTION The present invention relates to a method for heat-sealingorganic thermoplastic polymeric materials and, more particularly, isdirected to a novel sealing method for heatsealing film structures offluorocarbon polymeric material about large roll structures.

The heat-sealing of organic thermoplastic polymeric materials by theapplication of heat and pressure is a well known method for uniting suchmaterials to provide integral structures thereof such as, for example,tubular film structures. For instance, a flat sheet, web or filmstructure of organic thermoplastic material may be formed into a tubularstructure by contacting two opposed edges thereof in either abutting oroverlapping relation and heatsealing or welding the polymeric materialalong the line of contact thereof as by the application of suitable heatand pressure thereto to effect fusion and joining of the polymericmaterial thereat. The foregoing heat-sealing technique is especiallyuseful for forming large tubular film structures of heat-shrinkablepolymeric materials that are adapted to be installed upon large rollerelements and heatshrunk thereon to provide a covering on such rolls ofsuch suitable and desirable polymeric material. For example, each of US.Pats. 3,426,118 and 3,426,119 discloses a method for applying a tubularfilm of fluorinated ethylene polymeric resin onto the surface of largediameter rollers by heat-shrinking an integral tubular film thereonwherein the tubular film was fabricated from a flat sheet of polymericresin by abutting two opposed edges of the flat sheet and applying heatand pressure to the region of the abutting film edges to fuse and jointhe polymeric material thereat and provide a tubular film structure. Onemajor drawback and disadvantage of the heat-sealing apparatus and methoddescribed in the aforementioned patents resides in the impracticabilitythereof for forming a tubular film structure from a flat film structurein-situ on a large diameter roller element.

According to the present invention there is provided a method forheat-sealing tubular film structures of organic polymeric materialin-situ on large diameter roll structures which comprises wrapping aflat film or sheet of heat-shrinkable organic polymeric material,preferably fluorocarbon polymeric material, around said roll structure;contacting opposed edges of said film; spot-tacking the lapped edges atlongitudinally spaced points; maintaining said opposed edges secured infirm contact in a sealer bar assembly and heating the static sealer barthereby to heat said contacting opposed edges of said film and fuse andjoin the same whereby to form a unitary tubular film structure whichcircumscribes said roll structure; and thereafter applying heat to saidtubular film structure thereby to shrink said tubular film structureinto intimate contact with the surface of said roll structure forproviding a covering on the surface of said roll structure.

In earring out the method of the present invention, there is furtherprovided a heat-sealing device, hereinafter referred to as a staticsealer bar, comprising a body or base member having a recess on onesurface thereof, said recess extending substantially the entire lengthof said surface; an electrical resistance-type heating element disposedin said recess; a first layer of high temperature resistant materialoverlying said surface of said base memher; a layer of high temperatureresistant elastomeric-type material overlying the exposed surface ofsaid first layer of high temperature resistant material; and preferablya second layer of high temperature resistant material overlying theexposed surface of said layer of high temperature resistantelastomeric-type material. The layer of high temperature resistantelastomeric-type material may be replaced by a thin metallic bandpreferably of stainless steel. This latter embodiment of the staticsealer bar is especially useful for heat-sealing thin film structures ofpolymeric material, e.g., film structures that are below about 10 milsin thickness.

The nature and advantages of the method of the present invention will bemore clearly understood from the following description and the severalviews illustrated in the accompanying drawings wherein like referencecharacters refer to the same parts throughout the several views and inwhich:

FIG. 1 is a perspective semi-diagrammatic illustration of a multiplelarge roll installation whereat the roll covering method of theinvention finds utility;

FIG. 2 is a side sectional view illustrating the method of heat sealingthe film in-situ on a large diameter roll with a radially extending lapseal, with the sealer bar being relatively enlarged for clarity;

FIG. 3 is a side sectional view similar to FIG. 2 illustrating aslightly different arrangement of sealer bar means;

FIG. 4 is an enlarged fragmentary view of the sealer bar means of FIG. 3prior to the application of pressure thereto;

FIG. 5 is an enlarged fragmentary view of a further form of sealer barmeans in carrying out the invention;

FIG. 6 illustrates the sealer bar means of FIG. 4 under pressure;

FIG. 7 illustrates the sealer bar means of FIG. 5 under pressure;

FIG. 8 illustrates the sealed film about the roll subsequent to theremoval of the sealer bar means; and

FIG. 9 illustrates the sealed sleeve in tight shrink fit about the roll.

Heretofore in covering rolls and. other tubular members withfluorocarbon or similar sleeves it has been customary to prefabricatethe sleeve at a suitable facility, transport the sleeve to the site ofthe roll or rolls to be sleeved, remove the roll to be sleeved from itsbearing mounts, and telescope and sleeve over the roll. Thereafterfollowing any final treatment, the covered roll would be reattached inits mounts.

One reason for oif-situ prefabrication of the sleeves as heretoforeperformed is the relative dilficulty of achieving a satisfactory heatseal with hard-to-handle materials such as fluorocarbon polymers. Theunique seal bar 10 described at length in the parent application to beissued as Pat. 3,660,210, however, reliably effects the longitudinalseal S of the polymeric material when utilized in conjunction with thedisclosed handling and clamping technique of the subject invention,whereby on-site sleeving of rolls can now be economically, efficientlyand reliably carried out.

The importance of on-site sleeving can be realized when it isappreciated that rolls as at R in FIG. 1 as employed in textilefinishing mills, paper driers, printing apparatus and the likefrequently have a length on the order of \10, 20 or 30 feet, and adiameter around 3 to 4 feet or so. Just one such roll or drying can in apaper mill may well weigh up to 20 tons in having a one inch thick steelwall to withstand steam pressures on the order of 300 p.s.i. Further itshould be realized that in the paper industry it is not uncommon to have50 or 100 of such rolls in a single facility. As a consequence, themanpower and equipment downtime required to remove such massive rollsfrom their mount for telescopic association of a prefabricated sleevetherewith is considerable. The loss of several days is not uncommon.

In sharp contrast, the in situ seaming and sleeving of rolls R by thepresent invention completely eliminates the problem of dismantling theroll mounts, requires far less manpower, and equipment downtime isreduced to hours rather than days in providing coverings on the rolls R.The relative economies are nothing short of astonishing. This isespecially the case in paper mills wherein the Fourdrinier screenrequires periodic replacement. The

"screen can be replaced in eight hours or so, and during this relativelybrief down-time, a large roll can be sleeved with polymeric film inaccordance with my invention, whereby no additional time is lost. In thecourse of routine screen replacements, all dryer drums can be eventuallysleeved with the fluorocarbon polymer with resultant benefit to thepapermaking process as the sticky, clayey moist, freshly screened pulpno longer seeks to adhere to the dryer rolls.

As above indicated, the static sealer bars of the parent patent areespecially adapted for heat-sealing flat film or sheet structures ofpolymeric material in situ on large diameter roll structures. Theprocedure is depicted schematically in FIG. 2 which depicts a rollstructure R having a fiat film or sheet C of heat-shrinkable polymericmaterial such as fluorocarbon polymer wrapped therearound. One end offilm C passes under a static sealer bar whereas the other end of film Cpasses over a similar static sealer bar 10 and the edges of the film areoverlapped slightly and firmly secured in intimate contact between thestatic sealer bars 10, 10. A useful technique for maintaining the edgesof film in overlapped relation prior to clamping and full longitudinalscaling is to spot weld the overlapped film along the region of overlap.This may readily be done with an electric resistance-heated solderinggun, and is very advantageous for initially maintaining the overlappedfilm in proper alignment between the static sealer bars.

Static sealer bars 10, 10 exert or transmit a pressure force to the filmC held therebetween; the pressure force is provided by any suitablemeans such as a plurality of clamping devices 12. FIG. 2 also shows theuse of a protective element 14 of any suitable material such as wood ormetal which is interposed between a static sealer bar 10 and clamp 12and which provides a surface for contacting clamp 12 thereby protectingthe surface of film C. After installing the film C and static sealer barassembly 10 on a roll R, the static sealer bars are electricallyenergized thereby to heat the polymeric material in the region of thefilm that is secured therebetween. The heating is continued for a timesuflicient to effect plastic flow of the polymeric material and toobtain fusion at S, FIG. 8, of the polymeric material in the region ofthe film that is held between one or two static sealer bars 10. The timefor heating will depend of course upon such factors as the thickness ofthe film structure and may readily be determined by anyone skilled inthe art. Ordinarily, heating times of about 10 minutes and about 2'5minutes are satisfactory when utilizing fluorocarbon polymer films C ofabout 10 and about 20 mils thickness, respectively. Thereafter, thestatic sealer bar or bars 10 are de-energized and the film heldtherebetween is allowed to cool while being maintained under pressure.After cooling, the static sealer bars are removed (FIG. 8) and theunitary tubular film C enwrapped on rolls R is heat-shrunk on the rollin the conventional manner by applying heat thereto as described in US.Pats. Nos. 3,426Jl18 and 3,426,149 to result in the sleeved roll of FIG.9.

In sheathing relatively larger and longer rolls, the sheer expanse andweight of the fluorocarbon polymer C result in substantialseam-separating forces as indicated by the downwardly directed arrows inFIG. 2. This adverse effect is reduced by the practice of wrapping thefilm C about three sides of sealer bar 10 in FIG. 2, or sealer bar 16 inFIGS. 5 and 7. In this technique, the film C is clamped in a firstcircumferential zone along the length of the roll adjacent sealer bar 10at the overlapped film ends, and is also clamped at least at spacedintervals in a second circumferential zone along the roll by clampblocks 14. Desirably, the blocks 14 are substantially longitudinallycoextensive with the sealer bars.

In so disposing the inside member comprising the sealer bar 10 in FIG. 2or sealer bar 16 in FIG. 5 in the illustrated position, the inside baris initially slipped under the spot-tacked sleeve with the active faceof the bar disposed substantially tangentially of the drum. The outsidesealer bar 10 is then superposed on the film lap much as seen in FIG. 4.With the film lap now disposed within the sealer bar assembly, theinside and outside sealer bar members are gripped and turned to the FIG.2 or FIG. 5 position to dispose the film lapped edges substantiallyradially of the drum, after which the assembly is secured by the clamps12.

By this method whereby the film is partially rolled up on a bar with thelap disposed substantially radially of the roll R, (1) positive clampingforce can be exerted by the screw clamp or clamps 12, (2)seam-separating forces exerted on the initially spot-tacked film lap arenullified by blocks 14 and in view of the fact that pulling forcesexisting on the film adjacent block 14 cause the film to wrap tightlyagainst heater bar 10 or pressure bar 16 with less resultant shear forceeffective at the film lap, and (3) a full-length seam S of thedifiiculty seamed polymeric material C is achieved.

While in FIG. 2 two sealer bars 10 are shown between which the film lapis clamped, in the form shown in FIG. 5

one sealer bar 10 is replaced by a pressure bar 16. In essentialrespects, pressure bar 16 comprises a rigid support such as U-shapedchannel 18 within which is received an elongated inflatable bladder 20.Such an arrangement is generally known and is described more fully inPat. 2,960,147 to Ferrell.

Pressure bar 16 further includes a layer of high temperature resistantmaterial 22 of about 5 mils thickness which is preferably a polyimide,such as the material trademarked Kapton. Similar material is employedwith the sealer bars 10.

With this construction, after clamping, a uniform and predeterminedpressure may be applied along the length of the film lap by inflatingbladder 20 as desired from a suitable valved and controllable air source24 thereby to form an excellent seam S.

As indicated in FIG. 1, where the length of the roll being covereddictates, a plurality of heater bars 10 may be connected end-to-end withsuitable electrical connections therebetween and in external connectionto a source of controllable electric energy. Likewise, the bladders 20of adjacent pressure bar 16 may be connected as by tubing lengths 28. Ifthe roll length is in excess of the sealer bar assembly or assembliesavailable, the full length seal may be achieved in two or moresuccessive stages, advancing the seal bar along the lap.

With smaller rolls, or with film material of less bulk and weight, theslightly modified technique of FIGS. 3, 4 and 6 may be employed. Asshown, the film is not rolled up or wrapped around a seal assemblymember but merely lapped, spot-tacked and overlaid on sealer bar 10slipped therebcneath. Pressure bar 16 is superposed thereon.

In this method of sealing, clamp members 12 may not feasibly beemployed. The requisite clamping pressure is effected by the applicationof weights 30 upon the bar 16. Further pressure may be applied byanchoring a weight 30 in the form of an I-beam to the roll bearingmounts and tensioning the anchoring lines. Alternatively, the entireroll and seal assembly may be circumferentially banded or cinched withcables, care being taken to protect the sheath material as the cinch iscontracted to apply pressure to the seal assembly.

After formation and cooling of seal S, FIG. 8, the sealer bar assemblyis removed and the sleeve shrunk tightly onto the drum by theapplication of heat.

Heat may be provided from any convenient source such as a hot airblower. In the case of sheathing Yankee dryer rolls or the like, steamadmitted within the roll quickly and uniformly effects the desiredshrinkage.

To insure that there will be no relative rotation between the finishedsleeve C and roll R, or undesirable axial translation of the sleeve onthe roll, a suitable adhesive is applied at A, FIG. 9, between thecovering and the roll surface. The adhesive may be injected at severalpoints as by a needle, and thereafter the sheathed roll is squeegeed todisperse the adhesive substantially uniformly between the roll andsheath.

The preferred polymeric material utilized in the method of the presentinvention is a fluorocarbon polymer. The expressions fluorocarbonpolymer and fluorocarbon polymeric material as used herein meancopolymers of tetrafluoroethylene and hexafluoropropylene (PEP). Thefluorocarbon polymers are extensively described in patents such as, forexample, US. 2,833,686, US, 2,946,763 and U.S. 3,051,683.

What is claimed is:

1. A method for applying a tubular film covering of fluoropolymermaterial having a relatively high sealing temperature to an elongatedroll structure comprising the steps of:

wrapping a sheet of said material having heat-shrinkable propertiesaround said roll structure,

contacting opposed edge margins of said sheet along the length of saidroll structure,

gripping elongated portions of said sheet adjacent and upon saidcontacting edge margins thereof in an elongated static seal bar assemblyto maintain the contacting edge margins in fixed relation relative tosaid static seal bar assembly,

applying static clamping pressure at and through said contacting edgemargins without relative motion between said static seal bar assemblyand said edge margins while heating said contacting edge margins to atemperature fusing the contacting edge margins into an elongated seam,and

causing said seam to cool, thereby to form a unitary tubular filmcovering about said roll structure.

2. The method of Claim 1 wherein said fluoropolymer is PEP.

3. The method of Claim 1 including the step of dispos ing said opposedfilm edge margins in lapped relation.

4. The method of Claim 3 including the step of disposing the lapped filmedge margins in a plane substantially radially of the roll structureprior to heating and fusing of the film.

5. The method of Claim 3 including the step of applying clampingpressure across said lapped edge margins in a direction substantiallytangentially of the roll structure.

6. The method of Claim 3 including the step of applying clampingpressure across said lapped edge margins in a direction substantiallyradially of the roll structure.

7. The method of Claim 1 including the step of applying substantiallyuniform fluid pressure through said sealer bars.

8. The method of Claim 1 including the step of spot tacking the opposededges at intervals along their length prior to heating and fusing thesame.

9. The method of Claim 1 including the further step of heat-shrinkingsaid tubular film into intimate covering contact with said rollstructure.

10. The method of Claim 9 including the further step of injectingadhesive between the shrunk film and the roll.

11. A method for covering roll. structures with protective filmscomprising the steps of:

wrapping a sheet of a heat shrinkable, high sealing temperaturefluoropolymer around said roll, contacting opposed edge margins of saidsheet longitudinally of said roll structure,

spot-tacking said contacting edge margins at intervals along theirlength,

inserting a static seal bar member between said sheet edge margins andsaid roll structure along the length thereof to underlie said edgemargins radially of the roll,-

overlying a static seal bar member upon said edge margins along thelength thereof,

holding said seal bar members to secure firmly the contacting sheet edgemargins therebetween,

turning said seal bar members and thereby said clamped sheet edgemargins through substantially to dispose said sheet edge margins in aplane substantially radially of said roll,

heating said edge margins to a temperature sufficiently high to fuse andjoin the contacting edge margins, thereby to form a unitary tubular filmcovering about said roll structure,

cooling said fused margins,

unclamping and removing said seal bars, and

heat-shrinking said tubular film into intimate contact with said roll.

12. The method of Claim 11 including the further step of disposing abacking bar against the sheet portion adjacent the face of the insertedseal bar remote from the edge margins after the turning step, andclamping said backing bar to the seal bar assembly.

13. The method of Claim 1 including the steps of initially positioningthe static seal bar assembly on opposite sides of said contacting edgemargins along a line extending generally radially of said rollstructure, and thereafter turning said seal bar assembly and the edgemargins therein through substantially 90 to dispose the static seal barassembly on opposite sides of said contacting edge margins along a lineextending generally tangentially of said roll structure.

14. A method for heat sealing fluoropolymer films having a relativelyhigh sealing temperature to form a tubular film structure for sleeving aroll comprising the steps of bending a sheet of said fluoropolymer filminto a tubular configuration to dispose edge margins of said sheet inadjacent relation, gripping elongated portionsof said sheet adjacent andupon said edge margins thereof between opposed elongated members of aseal bar assembly,

rotating said seal bar assembly and the opposed film margins clampedtherein relative to the remainder of said tubular film through about 90to wrap the film about the surface of a seal bar member remote from thesurface thereof gripping said film edge margins,

applying an elongated member to the film overlying said wrapped seal barsurface,

7 clamping said elongated member, said seal bar assembly and the filmportions therebetween into a substantially rigid assembly, and heatingsaid edge margins to fuse and join the same into an elongated seam,thereby to form an elongated tubular fluoropolymer sleeve.

References Cited UNITED STATES PATENTS 8 Chapman et al l56 86 Irons156196 Holmes et al 15 6-86 Wilmotte et a1 156-580 Shoffner 15686CHARLES E. VAN HORN, Primary Examiner F. FRISENDA, JR., AssistantExaminer US. Cl. X.R.

